1. Field of the Invention
This invention relates to a semiconductor device and a manufacturing method thereof, and more particularly, to a semiconductor device in which the mobility is enhanced by embedding silicon germanium (SiGe) in source/drain regions of MISFETs and straining Si channels and a manufacturing method of the semiconductor device.
2. Description of the Related Art
As a manufacturing method of CMOS transistors having high drivability, the technique (so-called strained Si technique) for enhancing the mobility by straining silicon (Si) and applying stress to channel regions is known. Particularly, as one example of an element structure manufactured by the use of the strained Si technique, an eSiGe technique gains much attention. The eSiGe technique is a method for enhancing the mobility by embedding SiGe layers in the source/drain regions of pMISFET regions and applying compression stress to the Si channel regions (for example, refer to U.S. Pat. No. 6,621,131).
In the structure in which the SiGe layers are embedded in the source/drain regions of the pMISFET, stress to the channel region increases in proportion to the germanium (Ge) concentration in the SiGe layers. Therefore, the mobility is more enhanced as the Ge concentration becomes higher. However, since a risk caused by crystal defects in the SiGe layer becomes higher in proportion to the Ge concentration, there is a possibility that a problem of abnormal growth of salicide or junction leak (J/L) will occur when the Ge concentration becomes high.
In an LSI, not only elements having high drivability but also elements having high reliability are required. When the Ge concentration in the SiGe layer is made higher in order to manufacture elements having the high drivability, a risk due to the crystal defects in the SiGe layer increases, and as a result, the high reliability cannot be attained. That is, in the conventional method, both of pMISFETs having the high drivability and pMISFETs having the high reliability cannot be formed together in one chip.